Trampoline is an exercise equipment to help training of body balance, reaction ability, dynamic vision and muscle flexibility. It also provides appropriate vibration during jumping and bouncing that is helpful to brain development of young people. The trampoline was developed and introduced about two hundred years ago. Initially it was often used in circus or acrobatic performances. Later it was used by U.S. Air Force to train air force pilots. It was designated as a formal competition item in the Olympics game held in Sydney. Nowadays it becomes a popular exercise in many countries such as Europe, U.S. and Japan.
While the trampoline can bring many benefits to users, it also has potential risks to the users during exercising. For instance, inexperienced users could lose control of center of gravity during jumping and result in deviation from the center of the trampoline, and bounce outside the exercise range of the trampoline. In serious conditions, users could even fall to the ground or hit other objects outside the trampoline and get injured, bruised or sprained. To prevent such accidents and exercise injuries from happening, a trampoline equipped with a surrounding net was developed. The surrounding net forms a movable space to confine users to jump within the surrounded area. FIG. 1 shows a conventional trampoline with the surrounding net. It usually has a framed bed 100 with a jumping area 101 to allow users jumping and bouncing thereon and a plurality of supporting posts 300 located on the periphery of the framed bed 100 to hold a surrounding net 200. The surrounding net 200 has a bottom rim 202 located on the circumference of the jumping area 101 and a top rim 201 connected to a top end 301 of each supporting post 300 by means of a bracing band 400. Thus the surrounding net 200 is stretched upright and around to form the jumping area 101 to confine users within a limited movable space without the risk of bouncing outside the trampoline.
However, during jumping and bouncing exercise, the users could inadvertently or incidentally pull and drag the top rim 201 and cause damage of the surrounding net 200. As a result, the surrounding net 200 has to be replaced frequently and almost becomes a consumable supply. And periodic repair and maintenance have to be performed that incur a significant expense. To remedy the aforesaid problem, an improvement has been proposed as shown in FIG. 2. It differs from FIG. 1 by having the top rim 201 connected to a bracing rack 500. The bracing rack 500 usually is made of sturdy material such as metal. With the top rim 201 connected to and supported by the bracing rack 500, deformation and damage caused by pulling and dragging can be prevented. However, the sturdiness of the bracing rack 500 reduces the buffer resilience of the top rim 201 resulting from deformation that might otherwise take place. Users could incidentally hook the bracing rack 500 and inflict physical injury, such as on necks and arms since the lack of the elasticity of the bracing rack 500. To overcome the drawback mentioned above, some trampolines have the bracing rack 500 made from glass fibers. The glass fibers have toughness to provide sufficient support and are bendable to offer appropriate buffer to protect users from injury.
While the bracing rack 500 made from glass fibers provides more desirable characteristics, it tends to suffer from elastic fatigue after using for a period of time under frequent pulling and dragging, and irrevocable deformation occurs. Repair and displacement cost are expensive. The durability is not desirable. Hence there is still room for improvement about the bracing rack 500 of the surrounding net 200 of the trampoline.